On food and cooking the science and lore of the kitchen ( PDFDrive ) 945

milk, a concentrated mass of protein and oil formed by coagulating the dissolved proteins with salts that yoke them and the protein-coated oil droplets together.. Bean curd was invented

milk, a concentrated mass of protein and oil formed by coagulating the dissolved proteins with salts that yoke them and the protein-coated oil droplets together Bean curd was invented in China around 2,000 years ago, was well known by 500 CE, and became a daily food beginning around 1300 Chinese bean curd is traditionally coagulated with calcium sulfate, Japanese bean curd and bean curd from coastal regions of China with what the

Japanese call nigari, a mixture of magnesium

and calcium salts left over when table salt, sodium chloride, is crystallized from seawater

Making Bean Curd To make bean curd,

cooked soy milk is cooled to about 175ºF/78ºC, then coagulated with calcium or magnesium salts dissolved in a small amount

of water The coagulation takes 8–30 minutes When the delicate, cloud-like curds have formed, the remaining “whey” is ladled off, or

the curd is broken up to release water and drained The resulting mass is then pressed for 15–25 minutes while still quite hot, around 160ºF/70ºC, in order to form a cohesive mass that’s around 85% water, 8% protein, and 4% oil In commercial production, the curd is cut into blocks, packaged in water, and the packages pasteurized by immersion in hot water

Soft or silken tofu, with a custard-like

texture, is made by coagulating the soymilk in the package so that the curd remains intact, full of moisture, and delicate

Freezing Bean Curd Tofu is one of the few

foods that can be usefully altered by freezing When it freezes, the coagulated proteins become even more concentrated, and the solid ice crystals form pockets in the protein network When the frozen curd thaws, the liquid water flows from the toughened spongy network, especially when the curd is pressed